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Since taking Full backups consumes lots of space and also takes much time,
many dba's resorts to incremental backup. The advantage of incremental
backups compare to Full backup is that it takes less time and also
consumes less space.

The main idea of incremental backups is that not all tables are changed
daily. So why take full backup daily it's sufficient to just take backup of changes rather than whole
database.

An Incremental Backup copies only those blocks changed since last
incremental or full backup. The incremental backup takes less time and
occupies less space then a normal full database backup.

The incremental backups in RMAN is much robust than incremental Export
of database using Oracle Export tool. The incremental export of database
copies all the tables changed since last complete export. So even if one
row in a big table containing millions of rows is changed then the whole
table is considered as changed and export tool will export the whole
table while taking incremental export.

Whereas if you are taking an incremental backup using RMAN then if one
row is changed in a big table then RMAN will copy only the changed block
containing the changed row instead of copying the whole table blocks.

So the RMAN incremental backups are much more efficient and also takes
less time and occupies less space then incremental export of database

The increment backup in RMAN is done if you specify a
LEVEL <n> option,
where n can by either 0 or 1

In incremental backup strategy you will first need to take complete
backup i.e. LEVEL 0 backup

In the above picture, we are taking complete backup on Monday and then
on each other day of the week we are taking incremental backup. If we
lose the database on Friday in the first week, the database have to
recovered first from complete backup taken on first Monday and then we
have to apply the incremental backups taken on Tue, Wed and Thursday.

Similarly if the database is lost on Wednesday in the second week, we
have to recover database first from Monday in the second week and then
we have to apply incremental backups on Tuesday.

Let's take complete Backup LEVEL 0 backup

Type the following command at RMAN prompt

RMAN> backup incremental level 0 database;

The above backup can now be considered as base backup or parent backup.

Next day we can take incremental level 1 backup which will copy only
the changes made since last backup

To make incremental level 1 backup give the following command

RMAN> backup incremental level 1 database;

Similarly you can also take cumulative backup by typing the following
command

RMAN> backup incremental level 1 cumulative database;

You can also take incremental backup of particular tablespaces.

To take incremental backup of users tablespaces we can give the
following command